To satisfy the standards relating to the limit of disturbances in the network by electrical apparatus which are of the resistive or inductive type or a combination of these two types, the applicant has previously described a first control process which is the object of French patent application filed under No. 94 12833.
In such a process, for a previously set nominal value, there is delivered successively to said load, periodically a sequence of a whole number p of elements, p being greater than one, each element, of number i, of the sequence being characterized by the whole number n.sub.i of periods T during which the ac voltage U is symmetrically chopped at a phase angle .alpha..sub.i corresponding to a duration t.sub.i during which the load is not supplied, the consecutive phase angles .alpha..sub.i of the element i and .alpha..sub.i+1 of the element i+1 being different and the combination of the angles .alpha..sub.i . . . .alpha..sub.i . . . .alpha..sub.p being selected such that it satisfies the standards.
This first control process could give rise in certain cases of use and particularly in electrical motors, of mechanical vibrations due to the cycle of modulation of the phase angles.